Effects of Insulin and Procaine Hydrochloride on Glycogen Synthetase Activation and Adipocyte Calcium Flux: Evidence for a Role of Calcium in Insulin Activation of Glycogen Synthetase
- 1 January 1976
- journal article
- research article
- Published by Georg Thieme Verlag KG in Hormone and Metabolic Research
- Vol. 8 (03) , 184-190
- https://doi.org/10.1055/s-0028-1093657
Abstract
Observations that insulin-induced stimulation of glycogen synthetase occurs without detectable reduction in cyclic AMP suggests an alternative controlling mechanism. The hypothesis that this stimulation might be mediated through calcium was tested using procaine HCl, a drug whose insulin-like action is not associated with reduction in basal or adrenaline-stimulated cyclic AMP levels. Pretreatment of adipose tissue with insulin or procaine for 30 minutes increased homogenate glucose-6-phosphate independent ("I") form activity by 58% and 48% respectively with no significant change in total activity. Insulin and procaine also had similar effects on calcium efflux from isolated rat adipocytes. Following an initial displacement of calcium from the adipocytes by insulin (but not by procaine) both agents decreased efflux of calcium, measured following 10, 20 and 30 minutes incubation. In adipose tissue homogenates increasing the free calcium concentration from 10-8 to 10-3M increased "I" form glycogen synthetase activity without significantly altering total activity. A complex interrelationship with ATP and calcium was also observed. In the presence of ATP 0.5 mM maximal activation occurred at 10-6M calcium whereas ATP inhibited "I" form activity at 10-3M free calcium concentration. These findings suggest that insulin-induced activation of glycogen synthetase may be effected by alteration of intracellular free calcium with consequent effects on glycogen synthetase-related enzymes in a mechanism independent of or complementary to effects on cyclic AMP levels.Keywords
This publication has 9 references indexed in Scilit:
- Effects of insulin treatment on muscle 3′,5′-cyclic adenylate levels in vivo and in vitroBiochimica et Biophysica Acta (BBA) - General Subjects, 1967
- Competitive Action of Calcium and Procaine on Lobster AxonThe Journal of general physiology, 1966
- Effect of Insulin on Adenosine 3‘,5‘-Monophosphate in the Rat Epididymal Fat PadJournal of Biological Chemistry, 1966
- The dependence of contraction and relaxation of muscle fibres from the crab Maia squinado on the internal concentration of free calcium ionsBiochimica et Biophysica Acta (BBA) - Specialized Section on Biophysical Subjects, 1964
- Fatty acid esterification and release as related to the carbohydrate metabolism of adipose tissue: Effect of epinephrine, cortisol, and adrenalectomyArchives of Biochemistry and Biophysics, 1964
- METABOLISM OF ISOLATED FAT CELLS .I. EFFECTS OF HORMONES ON GLUCOSE METABOLISM + LIPOLYSIS1964
- THE DISTRIBUTION AND KINETICS OF RELEASE OF RADIOCALCIUM IN TENDON AND SKELETAL MUSCLEThe Journal of general physiology, 1959
- PROTEIN MEASUREMENT WITH THE FOLIN PHENOL REAGENTJournal of Biological Chemistry, 1951
- Factors influencing deposition of glycogen in adipose tissue of the ratThe Journal of Physiology, 1946